Why does the Earth exert a gravitational force on objects on its surface? A. It has an atmosphere,
B. It has mass
C. It has a magnetic field.
D. It is so dense.

B. It has mass

Explanation:

The Newtons Universal gravitacion law is : F = G.  , where F is the force exerted , m1 and m2 are the earth's mass and the object's mass, d is the distance and G the gravitacional constant. Comparing to the options we can say that the Earth exerts a gravitational force on objects on its surface because of its mass.

the moon affects the earth gravitation ally, causing certain motions of that body and also producing tides in its ocean and atmosphere. the tidal wave in our atmosphere is, however, far too minute to be an effective cause in any known meteorological phenomenon.

explanation:

i am pretty sure it is c because when people are closer together, they cannot move as freely. picture being in a mostly full elevator, for instance. the people are right next to you, and you can barely move.